The effects of Rhizoctonia solani on the hypocotyls of resistant and susceptible lines of lima bean were studied . The fungus attacks lima bean at one or more stages during host development and causes pre-and -postemergence damping-off, root rot, and foliage blight. The isolate of the fungus used in this study was obtained from infected radishes grown in Salt Lake County. Utah.
The formation of infection cushions and modes of penetration by this fungus was no different on the resistant and susceptible lima bean hypocotyls . The infection process was studied under laboratory conditions . Differential staining showed that the fungal hyphae were closely appressed to the host surface , and at first along the longitudinal axis o f the epidermal cells. Later, hyphal branches grew in oblique and transverse directions . Aggregated hyphal tips formed infection cushions , which gave rise to one or more infection pegs that penetrated the host directly . Following penetration, both intercellular and intracellular hyphae were formed. The build-up of masses of hyphae occurred as club-shaped structures in the cortex of the susceptible lima bean hypocotyls , but were not observed in the resistant hypocotyls . The extents of infection in the resistant and susceptible lima bean hypocotyls were different at 7 days after inoculation. The hyphae in the susceptible hypocotyl had penetrated into vascular bundles and pith , whereas the hyphae had penetrated the cortex and pith of the resistant hypocotyl but were not observed in the vascular tissue.
Stomatal penetration from individual hyphal side branches was rare and apparently of minor importance as a means of penetration by this isolate .
| Identifer | oai:union.ndltd.org:UTAHS/oai:digitalcommons.usu.edu:etd-4235 |
| Date | 01 May 1969 |
| Creators | Bunnag, Chulevan |
| Publisher | DigitalCommons@USU |
| Source Sets | Utah State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | All Graduate Theses and Dissertations |
| Rights | Copyright for this work is held by the author. Transmission or reproduction of materials protected by copyright beyond that allowed by fair use requires the written permission of the copyright owners. Works not in the public domain cannot be commercially exploited without permission of the copyright owner. Responsibility for any use rests exclusively with the user. For more information contact Andrew Wesolek (andrew.wesolek@usu.edu). |
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